For many who take into consideration the rising universe identical to the ground of a balloon, you presumably can see that as a result of the balloon (our stand-in for space-time) expands, galaxies are carried along with it. On account of space-time itself is rising, the universe simply is not rising into one thing. Credit score rating: Astronomy: Roen Kelly
What is the universe rising into?
Euan Tobin
Edinburgh, Scotland
This glorious question forces us to confront a space previous the bounds of our intuition, so please bear with me. When you inflate a balloon, the balloon’s membrane strikes outward, nearer to the boundaries of irrespective of room encloses it. You presumably can merely visualize this enlargement because of one object is inflating relative to a set enclosure.
The notion of the enlargement of the universe is additional problematic because of the universe contains each half — it is a closed space-time system. One could say that the universe isn’t rising into one thing because of the question implies that one factor exists “exterior” the universe, which is nonsensical, as “exterior” is a spatially relative time interval.
Nonetheless, such an answer is unsatisfactory. Let’s return to the balloon. This time, let’s draw a set of black dots alongside the membrane. As a result of the balloon inflates, the dots seem to be transferring away from each other. From the angle of 1 dot, the additional distant dots switch away additional quickly than these nearer to it. As a result of the membrane expands, the dots develop farther apart. On this occasion, the dots symbolize the galaxies, whereas the membrane represents the finite however unbounded universe. You presumably can journey alongside the balloon nevertheless certainly not come to the “end,” because it’s really unbounded. And though the balloon’s ground will not be infinite in extent, it isn’t outlined by an outer boundary. (Observe {{that a}} shortcoming of this balloon analogy is that it tries to represent three-dimensional actuality alongside a two-dimensional shell.)
Frequent enlargement causes galaxies to recede from each other. Galaxies close to us recede at a slower worth than these farther away. As demonstrated by the balloon model, the space-time “material” is what’s rising, and the material embedded inside it — significantly galaxies — strikes apart in response to this enlargement. We cannot actually say that the universe is rising “into” something. There is no mounted coronary heart, neither is there any rigid outer boundary. It is merely rising, just because the balloon membrane expands — albeit in three spatial dimensions instead of two.
Edward Herrick-Gleason
Astronomy Educator, St. John’s, Newfoundland and Labrador